Conventionally, for use of a back-monitor of a vehicle, an high sensitive imaging apparatus capable of obtaining a color image has been known. Recently, multifunctional imaging apparatus capable of, for example, imaging a polarized image for detecting a wet state of a road surface with a high sensitivity has been required.
In a conventional technique, when a color image or a polarized image is obtained, methods for demosicing an obtained image by providing a color filter on each pixel of the imaging element (see, for example, Japanese Patent Application Publication No. 2000-278503), or disposing a micro-polarizer (see, for example, Japanese Patent Application Publication No. 2007-86720) has been generally used.
However, for example when a RGB primary color filter is used, simply, a light amount received by each pixel is reduced to one-third of a light amount in a case where the filter is not used. Furthermore, in a case where a polarizer is used, since only a light amount of either P-polarized light or S-polarized light, that is, ½ of total light amount is received by each pixel, the light amount received by each pixel is reduced to ½ of light amount in a case where the filter is not used is received by each pixel. Therefore, there is a problem in that sensitivity is degraded in principle. Furthermore, resolution of brightness information is degraded compared to the case where the filter is not used, so that low resolution of an obtained image is visible to the human eyes.
In order to solve the above problems, regarding a filter array to obtain an color image, for example, it has been proposed that pixels without filter are added to a color filter array in order to obtain brightness information with the fact that sensitivity of the human eyes to brightness signals is higher than that to color signals (see Japanese Patent No. 4144630).
However, in the above conventional technology, there are problems in that, for example, when combining the brightness information and the color information, if a sampling period of the color information is small in relation to the brightness information, aliasing noise occurring in the color information causes degrade in a quality of an image so that ratio of the pixels without filter cannot be increased.
Furthermore, there is a problem in that due to a large difference between the receiving light amount of the pixel with a filter and the receiving light amount of the pixel without a filter, only the light amount of the pixel without filter is saturated so that normal color reproduction cannot be achieved.